The present invention relates in general to any indirect heat exchange between, on the one hand, a refrigerant or refrigerating fluid, for example a refrigerant (for example ammonia) in the course of vaporization, and, on the other hand, a fluid to be cooled, namely a liquid in the course of cooling and/or partial freezing, to the exclusion of any congealing of said fluid, such as of water containing glycol, alcohol or salt, the crystallization point of which is less than 0.degree. C.